public class WorkbookView 

using( var workbook = Workbook.Create( "test.xlsx" ) )
  {
    // Get the first worksheet. A workbook contains at least 1 worksheet.
    var worksheet_A = workbook.Worksheets[ 0 ];

    // Fill cells in 1st worksheet.
    worksheet_A.Cells[ "D5" ].Value = "This is the first Worksheet.";

    // Add a worksheet with default "SheetX" name.
    var worksheet_B = workbook.Worksheets.Add();

    // Fill cells in 2nd worksheet.
    worksheet_B.Cells[ "D5" ].Value = "This is the second Worksheet.";

    // Add a worksheet with name "Third Sheet".
    var worksheet_C = workbook.Worksheets.Add( "Third Sheet" );

    // Fill cells in 3rd worksheet.
    worksheet_C.Cells[ "D5" ].Value = "This is the third Worksheet.";
       
    // Assign the active worksheet to be the 2nd one.
    workbook.WorkbookViews[ 0 ].ActiveTab = 1;

    // Save workbook to disk.
    workbook.Save();
  }